1. Field of the Invention
The invention relates to the field of programmable pacemakers and in particular to devices used to reprogram cardiac pacemakers.
2. Description of the Prior Art
Many cardiac patients can enjoy healthier lives and longer life spans by artificially pacing their hearts. A pacemaker is subcutaneously implanted above the chest wall and a cardiac catheter or catheters are then led through a vein into the heart to implant or dispose a pacemaking tip in a predetermined position within the heart. The pacemaker then delivers a timed stimulating pulse to ensure that a regular heart rhythm is maintained. Early pacemakers had a fixed protocol or rhythm of stimulating pulses which they delivered to the heart. The sophistication of the pacemaker circuitry increased to provide different types of demand pacemakers which would provide a stimulating pulse only upon certain conditions or to alter the stimulating pulse depending upon the heart rates or other biophysical parameters such as respiration or activity.
The sophistication and flexibility of pacemakers has continued to rapidly expand to the point where pacemakers which are now implanted are typically reprogrammable, that is any one of a variety of cardiac pacing protocols can be programmed into the pacemaker even after it is subcutaneously implanted. The pacemaker thus becomes generally programmable and the cardiac pacing can be diagnostically changed as the patient's diagnosis changes or as his cardiac disease state improves or deteriorates.
Typically, the pacemaker is programmed by placing a radio frequency transmitter or programming head over the pacemaker, sometimes over a predetermined portion of the pacemaker such as the upper one-third. Various testing procedures are practiced to determine if the programming head is properly positioned relative to the pacemaker pulse generator. When programming is performed, it is important not to alter or reposition the programming head above the pacemaker. Such repositioning might cause failure of correct program transmission or incomplete programming.
In addition, any movement of the programming probe while positioned over the pacemaker may interfere with proper decoding of the telemetry signal received from the pacemaker. This in turn may result in the display of inaccurate pacemaker data transmission. Typically, programming of the pacemaker may require the retention of the programming head over the pacemaker for time period ranging from 5 to 25 seconds repetitively over 10 to 30 minutes. In most cases, the programming head is simply hand held over the pacemaker for this time period. In most case, the technician is able to adequately maintain the programming head in a fixed or still position relative to the pacemaker. However, the number of instances in which movement of the programming head relative to the pacemaker does occur and the consequences of a deleterious effect either on the pacemaker, the patient, or both of such movement is great enough as to require additional security measures to be undertaken to ensure successful pacemaker manipulation. This is particularly the case when programming in the upright position or during exercise.
Therefore, what is needed is some type of means which may be used in connection with programmable pacemakers for positioning a device, such as a programming head over a predetermined position on the embedded pacemaker for a predetermined time without substantial risk of inadvertent relative movement between the two.